APPENDIX 

 THE BIOMETER: HOW TO USE IT 



The study of carbon dioxide has been so connected 

 with various forms of human activity that in spite of 

 natural difficulties methods for its accurate quantitative 

 determination have been highly developed. Never- 

 theless, none of the various methods of analysis can be 

 used for very minute quantities of carbon dioxide. The 

 greatest difficulty in using any micro-gas analysis is in 

 securing freedom from the external variations of tempera- 

 ture and pressure. Particularly is this so in the case of 

 carbon dioxide, for we need to consider, not only the 

 effect of temperature and pressure variation, but also 

 how to free the apparatus from atmospheric carbon 

 dioxide. After we discovered a new method which 

 detected exceedingly minute quantities of this gas we 

 found that the ordinary method of freeing air or any 

 other gases from carbon dioxide was not sufficiently 

 accurate, although it should be admitted that our 

 experience in washing gases was not very extensive. 

 The biometer is constructed with a view to meeting 

 these difficulties and has shown itself to be remarkably 

 convenient for many biological as well as chemical 

 investigations. 



Uses of biometer- -The biometer can detect carbon 

 dioxide in as small quantities as one ten-millionth of a 

 gram. This is the amount contained in one-sixth of a 

 cubic centimeter of the purest air, in which we assume 



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